tests: print the server error log in `test-url-download.t` There was a stray 500 error in CI, but no additional context to know what the issue was. https://foss.heptapod.net/octobus/mercurial-devel/-/jobs/163093 Differential Revision: https://phab.mercurial-scm.org/D9949

[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true